A centennial renewal of America's great immigration debate is under way. Skirmishes in recent years were just a prelude. The U.S. must decide again a fundamental question—is it enough to embody principles without common roots as a people?

History repeats. In the 1890s, amid a still-building rush of foreigners to U.S. shores, political groundwork was laid for what, over the next 30 years, would become tight curbs on entry to this country. The lid stayed on until 1965.

Since it came off, at least 20 million have entered and added babies. The reaction has finally come. In its current issue, National Review, the largest-circulation conservative magazine, devotes 16 pages to an argument against continued dilution of the traditional American stock. A more esoteric quarterly of the right, the National Interest, is doing much the same.

Off the radar screens of the mainstream media, a sometimes crude but legitimate (not KKK or skinhead) anti-immigration lobby has assembled in parts of the U.S. for more than a decade. Now it has made an intellectual breakthrough. It doesn't yet have a Saturday Evening Post, the primary restrictionist organ of the early 1900s, but it can no longer be ignored.

Why is this news? After all, conservatives rarely have been friendly to mass immigration. Border protection long has attracted an unusual mix of progressives, unionists and traditionalists. But as the National Review article laments, the establishment right in the U.S. generally has welcomed the multitudes over the past two decades. This fact is commonly ascribed to simple class exploitation, although for most in the idea trades it's been more an expression of resurgent classical liberalism that upholds unhampered exchange in nearly all its forms.

Open access to the Land of the Free has had no greater champion than this newspaper, and capitalist circles have basically applauded. Commercial interests apparently approved of the last influx as well—until about 1914, according to one scholar from the era, when disturbances linked to immigrants caused business to switch.

Today, too, it will matter whether the titans of finance and industry, and for that matter the shopkeepers (many of them foreign-born), join the current backlash. It cannot be said that National Review's author, Peter Brimelow, represents a convert to containment. The Forbes journalist has long had national integrity weighing on his basically libertarian mind. And by "nation," this soon-to-be-naturalized American (from Britain, via Canada) means the grouping of a like people. The U.S., by this standard, is ever further from being one nation.

Even further, argues Mr. Brimelow, than during the peak influx of 1901-1910. By any measure, the ethnic composition of the U.S. is undergoing a dramatic shift because of the new arrivals and their usually higher fertility rates. One alarmed specialist projects barely 60% of the overall population will be non-Hispanic white by 2020.

To Mr. Brimelow and some others on the right, this foretells a changed U.S. character and economic deterioration, as nations with endemically lower levels of scholarship and output constitute more of the American mix. Such sentiment was part of the mainstream debate even 50 years ago, but the establishment right until lately had banished any whiff of racial ranking to the fringes.

Renewed emphasis on origins and limits could herald an attack on both the quotas for legal immigration, which with refugee and asylum cases now number nearly a million a year, and on illegal entries, totals unknown.

Legal slots could be tailored more to the types of immigrants considered likely to be successful in the U.S., because of skills or schooling or existing wealth or their home country's track record. This screening, particularly the last kind, offends those who think an individual's initiative to hazard a long trek and border crossing is measure enough.

In any case, preferences are no panacea. Canada and Europe employ them (while allowing refugees) yet are just as divided over immigration. Moreover, picking people who will add to the national wealth (and the values that support it) is no easier than choosing winning technologies. Were all those Koreans—or peasants who bred valedictorians—a good bet?

Meanwhile, illegal entrants aren't subject to the law's finer points. Barring and uprooting them is likely to come down to firepower, and the will to threaten it on borders and in cities.

For businesses relying on legal and illegal low-wage labor, such a push would change the terms of trade. Few could expect to find replacements at anywhere near the going wage, if at all. Mr. Brimelow & Co. say too bad, cheap workers discourage capital investment.

The claim that sustainable jobs are being taken by immigrants, or more believably that unskilled wage levels are depressed by the alien pool, is still alive. However, the dominant concern in middle-class America, whose votes will ultimately decide the issue, is the dependency associated with immigration: welfare, schools, medical care and jails (see a related beef: crime).

Those factors were all raised in the last great debate, but with the quantum growth in government since, they are now controlling. Unless drastic steps are taken to reduce the uniform level of taxpayer-provided services, immigrants are likely to be singled out to take the cuts full force.

Likewise, the perceived failure to assimilate into American life, attributed to virtually every immigrant group at one time or another, has been given new importance by the multiculturalism movement. The last time around, "Americanization" campaigns, supported by powerful U.S. civic institutions, sought unevenly to address this. Properly handled, encouraging inclusion and citizenship, they could ameliorate current conditions.

Another way to rub the left wrong but hold the right tight would be to emphasize a temporary worker visa program. "Bracero" has a bad name, but a formal entry channel that allowed law-abiding, self-sufficient workers to build up points toward permanent residency and family resettlement could appeal as a compromise.

When U.S. prosperity subsides, so does immigration historically. Still, no surcease is likely to keep immigration from being a political battleground, absent other preoccupations. If there is a wish in 1992 to "take America back" from some alien force, it is easy to see the literal connection being drawn. Pat Buchanan appeared to get some response to his anti-immigrant ads in California, and Texas Sen. Phil Gramm is talking up the issue for later.

My hunch is that it comes to a head sooner, in a tight race for the White House this November. Despite his recent bow to the "melting pot," I can see it sewn into the nationalism of H. Ross Perot.